Among standards of multimedia interfaces between a video transmission device and a video receiving device is the HDMI (high-definition multimedia interface; registered trademark). Video transmission devices having an HDMI output terminal are called source devices and video receiving devices having an HDMI input terminal are called sink devices. Source devices are equipped with an HDMI LSI which functions as an HDMI transmission unit and a video processing LSI which outputs decoded video data to the HDMI LSI. Sink devices are equipped with an HDMI reception LSI and a video processing LSI for processing video data that is output from the HDMI reception LSI and thereby generating a video signal to be supplied to a display device. Inside source devices and sink devices, the HDMI LSI and the video processing LSI are connected to each other by a prescribed interface and video data is exchanged through the interface.
When information that is different from conventional video data comes to be transmitted through the interface between an HDMI LSI and a video processing LSI, it will be desired to transmit such information efficiently.